I had a villager trading hub that had various villages grouped into several places (one for farmers, one for stonecutters etc.) When I had gone mining for couple of minecraft days, I gone back to stonecutters to trade regular stone for emerals. When I arrived for trades, all I find was baby villagers. At first I thought that villagers had babies and that's what they are but all my villagers that had work stations have been replaced by babies with the exact same amount. Why did they turned back into babies? I am not mad, since I wanted to change a few of their trades and this gives me an opportunity, but still I got very confused finding nearly 20 baby villagers instead of max level farmers.